Conventionally, there is a known tire testing machine for measuring rolling resistance of a tire, including a spindle shaft for holding a tire, a housing for rotatably supporting this spindle shaft through a bearing, a running drum for making the tire run by rotational driving, and a load cell provided in the housing for measuring a force generated in the tire. However, in such a tire testing machine, the spindle shaft is rotatably supported on the housing or the like through the bearing. Therefore, the fact is that when the spindle shaft is rotated (when the tire runs), a rotational friction torque is unavoidably generated in the spindle shaft by rotational friction of the bearing. In such a tire testing machine, the rolling resistance is measured in a state that a torque similar to the rotational friction torque is imparted onto the center of the tire through the spindle shaft. Therefore, there is a problem that a measurement value of the rolling resistance is different from the rolling resistance of the tire in the original state of freely rolling.
A trial to this problem is described in the related art document. For example, Patent Document 1 discloses a measurement method of rolling resistance of a tire for theoretically correcting a value measured by a load cell so as to eliminate an impact of a rotational friction torque by a bearing. Specifically, the method described in Patent Document 1 includes preliminarily setting a matrix (a transformation matrix) for correcting the measurement value measured by the load cell by means of calculation, and correcting the measurement value measured by the load cell based on the matrix so as to eliminate the rotational friction torque (disturbance).
However, this method is not to solve the problem that the tire is not in the original state of freely rolling. That is, even when the measurement value of the load cell is corrected so as to obtain the rolling resistance as in this method, the correction is only performed in theory, and hence the obtained value is different from actual tire rolling resistance. Furthermore, Patent Document 1 does not disclose any specific correction method. Therefore, it is highly difficult to measure the rolling resistance of the tire with high precision.    [Patent Document 1] Japanese Patent Laid-Open No. 2003-4598